New 4-substituted azetidinones having the formulea I and II: ##STR1## with R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and X defined hereafter, which are intermediates for the preparation of carbapenem and carbacephem antibacterials and processes for producing such antibacterials through the utilization of an acid mediated ring closure reaction.
具有以下式子I和II的新4-取代氮杂
丁酮:##STR1## 其中R.sup.1,R.sup.2,R.sup.3,R.sup.4,R.sup.5和X的定义如下,它们是制备碳青霉烯和碳头霉素抗菌剂的中间体,并通过利用酸介导的环合反应制备这些抗菌剂的过程。